ORACEL和mysql的数据类型存在较大差异（如Oracle的number和mysql的decimal（）
导致我们在数据迁移的时候有不小的麻烦
即使我们使用navicat的同步工具，同步表结构和数据，自动生成的字段类型也并不都是我们想用的，如Oracle的interger 同步过来到mysql变成了decimal（65,30），显然不是我们想要的；
于是乎，参考网上的sql写了一个自定义函数，
调用方式为 select fnc_table_to_mysql（‘’用户名’，‘表名’）from dual;
就可以得到一段创建mysql表结构的SQL。
create or replace function fnc_table_to_mysql
( i_owner in string,
i_table_name in STRING
)
/*
已知问题：
1.不支持分区
2.不支持函数索引，位图索引等特殊索引定义
3.不支持自定义数据类型，不支持ROWID,RAW等特殊数据类型
4.不支持外键
5.不支持自定义约束
6.不支持与空间、事务相关属性
7.TIMESTAMP转换成datetime，需注意精度
8.超大NUMBER直接转换为bigint，需注意精度
*/
return clob is
Result clob;
cnt number;
data_type varchar2(128);
column_str varchar2(4000);
-- pk_str varchar2(4000);
table_comments varchar2(4000);
is_pk_column number := 0;
begin
select count(*)
into cnt
from all_tables
where owner = UPPER(i_owner)
and table_name = UPPER(i_table_name);
if (cnt = 0) then
RAISE_APPLICATION_ERROR(-20000,'can''t found table,please check input!');
else
Result := 'CREATE TABLE `' || lower(i_table_name) || '`(
';
--column
for c in (select a.column_name,
a.data_type,
a.data_length,
a.data_precision,
a.data_scale,
a.nullable,
a.data_default,
b.COMMENTS
from all_tab_cols a, all_col_comments b
where a.owner = UPPER(i_owner)
and a.table_name = UPPER(i_table_name)
and a.HIDDEN_COLUMN = 'NO'
and a.owner = b.OWNER
and a.TABLE_NAME = b.TABLE_NAME
and a.COLUMN_NAME = b.COLUMN_NAME
order by a.column_id) loop
if (c.data_type = 'VARCHAR2' or c.data_type = 'NVARCHAR2') then
data_type := 'varchar(' || c.data_length || ')';
elsif (c.data_type = 'CHAR' or c.data_type = 'NCHAR') then
data_type := 'varchar(' || c.data_length || ')';
elsif (c.data_type = 'NUMBER') then
if (c.column_name like '%ID' and c.data_scale is null) then
data_type := 'bigint';
elsif (c.data_precision<3 and c.data_scale = 0) then
data_type := 'tinyint';
elsif (c.data_precision<5 and c.data_scale = 0) then
data_type := 'smallint';
elsif (c.data_precision<10 and c.data_scale = 0) then
data_type := 'int';
elsif (c.data_precision is not null and c.data_scale = 0) then
data_type := 'bigint';
elsif (c.data_precision is not null and c.data_scale is not null) then
data_type := 'decimal(' || c.data_precision || ',' ||
c.data_scale || ')';
else
data_type := 'decimal(32,4)';
end if;
elsif (c.data_type = 'DATE' ) then
data_type := 'date';
elsif (c.data_type = 'DATETIME' OR c.data_type like 'TIMESTAMP%') then
data_type := 'datetime';
elsif (c.data_type = 'CLOB' or c.data_type = 'NCLOB' or
c.data_type = 'LONG') then
data_type := 'text';
elsif (c.data_type = 'BLOB' or c.data_type = 'LONG RAW') then
data_type := 'blob';
elsif (c.data_type = 'BINARY_FLOAT') then
data_type := 'float';
elsif (c.data_type = 'BINARY_DOUBLE') then
data_type := 'double';
else
data_type := c.data_type;
end if;
column_str := ' `' || lower(c.column_name) || '` ' || data_type;
if (c.column_name like '%ID' and
(c.data_scale is null or c.data_scale = 0)) then
select count(*)
into is_pk_column
from all_constraints a, all_cons_columns b
where a.owner = UPPER(i_owner)
and a.table_name = UPPER(i_table_name)
and a.constraint_type = 'P'
and a.OWNER = b.OWNER
and a.TABLE_NAME = b.TABLE_NAME
and a.CONSTRAINT_NAME = b.CONSTRAINT_NAME
and b.COLUMN_NAME = c.column_name;
if is_pk_column > 0 then
column_str := column_str ;
end if;
end if;
if c.nullable = 'NO' then
column_str := column_str || ' NOT NULL';
end if;
if (trim(c.data_default) is not null) then
column_str := column_str || ' DEFAULT ' ||
trim(replace(replace(c.data_default, chr(13), ''),
chr(10),
''));
end if;
if c.comments is not null then
--column_str := column_str || ' COMMENT ''' || c.comments || '''';
column_str := column_str || ' COMMENT ''' || c.comments || '''';
end if;
Result := Result || chr(10) || column_str || ',';
end loop;
--pk
for c in (select a.constraint_name, wm_concat(a.column_name) pk_columns
from (select a.CONSTRAINT_NAME,
'`' || b.COLUMN_NAME || '`' column_name
from all_constraints a, all_cons_columns b
where a.owner = UPPER(i_owner)
and a.table_name = UPPER(i_table_name)
and a.constraint_type = 'P'
and a.OWNER = b.OWNER
and a.TABLE_NAME = b.TABLE_NAME
and a.CONSTRAINT_NAME = b.CONSTRAINT_NAME
order by b.POSITION) a
group by a.constraint_name) loop
Result := Result || chr(10) || ' PRIMARY KEY (' ||
lower(c.pk_columns) || '),';
end loop;
--unique
for c in (select a.constraint_name, wm_concat(a.column_name) uk_columns
from (select a.CONSTRAINT_NAME,
'`' || b.COLUMN_NAME || '`' column_name
from all_constraints a, all_cons_columns b
where a.owner = UPPER(i_owner)
and a.table_name = UPPER(i_table_name)
and a.constraint_type = 'U'
and a.OWNER = b.OWNER
and a.TABLE_NAME = b.TABLE_NAME
and a.CONSTRAINT_NAME = b.CONSTRAINT_NAME
order by b.POSITION) a
group by a.constraint_name) loop
Result := Result || chr(10) || ' UNIQUE KEY `' ||
lower(c.constraint_name) || '`(' || lower(c.uk_columns) || '),';
end loop;
-- index
for c in (select a.index_name, wm_concat(a.column_name) ind_columns
from (select a.index_name,
'`' || a.COLUMN_NAME || '`' column_name
from all_ind_columns a
where a.table_owner = UPPER(i_owner)
and a.TABLE_NAME = UPPER(i_table_name)
and not exists
(select index_name
from all_constraints b
where a.TABLE_OWNER = b.owner
and a.TABLE_NAME = b.TABLE_NAME
and a.INDEX_NAME = b.INDEX_NAME)
order by a.COLUMN_POSITION) a
group by a.index_name) loop
Result := Result || chr(10) || ' KEY `' || lower(c.index_name) || '`(' ||
lower(c.ind_columns) || '),';
end loop;
Result := substr(Result, 1, length(result) - 1) || chr(10) || ')';
--table comments
select max(a.COMMENTS)
into table_comments
from all_tab_comments a
where owner = UPPER(i_owner)
and table_name = UPPER(i_table_name);
if (table_comments is not null) then
Result := Result || 'COMMENT=''' || table_comments || '''';
end if;
Result := Result || ';';
end if;
return(Result);
end fnc_table_to_mysql;
参考于：https://blog.csdn.net/weixin_42531396/article/details/113123942?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522165207756116782246448404%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fall.%2522%257D&request_id=165207756116782246448404&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2allfirst_rank_ecpm_v1~rank_v31_ecpm-2-113123942-null-null.142v9control,157v4control&utm_term=mysql%E5%BB%BA%E8%A1%A8%E7%9A%84%E6%97%B6%E5%80%99%E5%8F%AF%E4%BB%A5%E7%94%A8trim%EF%BC%88%EF%BC%89%E5%90%97&spm=1018.2226.3001.4187
